1. Field of the Invention
Aspects of the present invention relate to a heater for heating a reformer of a fuel cell, and more particularly, to a heater for a fuel cell system, in which an igniter is provided inside a distributor that distributes a combustion fuel and an oxidant to a combustion catalyst layer in the case where a combustion catalyst is used in burning the combustion fuel, so that durability of the igniter is enhanced.
2. Description of the Related Art
In general, a fuel cell system is a power generation system that generates electricity through an electrochemical reaction between hydrogen and an oxidant. As an example of a fuel cell system, a polymer electrolyte membrane fuel cell (PEMFC) employs hydrogen produced by reforming a hydrogen-containing fuel. A PEMFC thus has advantages as compared with other types of fuel cells in that its output performance is excellent; its operation temperature is low; and its start and response are quickly performed. Further, the PEMFC can be used for a wide variety of purposes such as, for example, as a distributed power source for a house or a public building, as a small portable power source for portable electronic devices, etc., and as a transportable power source for vehicles.
A typical PEMFC system includes a fuel container to store hydrogen-containing fuel; a reformer to reform the hydrogen-containing fuel supplied from the fuel container and to produce hydrogen; and a fuel cell main body (hereinafter, referred to as a ‘stack’) to generate the electricity through an electrochemical reaction between hydrogen supplied from the reformer and oxygen.
As shown in FIG. 5, a reformer disclosed in Korean First Patent Publication No. 2004-0034026 comprises a preheater 10 to preheat water supplied from the outside; a mixing preheater 20 in which water preheated by the preheater 10 and hydrocarbonaceous gas supplied from the outside are mixed and preheated; a steam-reforming reaction unit 30 in which reaction gas preheated by the mixing preheater 20 absorbs heat and causes a steam-reforming reaction to produce hydrogen; and a burner 40 to provide heat for the endothermic reaction of the steam-reforming reaction unit 30. In the reformer, the preheater 10, the mixing preheater 20, the steam-reforming reaction unit 30 are manufactured to have a planar dimension such that they can be stacked with one another within a heat isolating reformer body 50. Specifically, the preheater 10, the mixing preheater 20 and the steam reforming reaction unit 30 are stacked from a top to a bottom of the reformer body 50 in sequence. The burner 40 is placed under the steam-reforming reaction unit 30. Further, two gas guiding plates 60 and 70 are provided between the preheater 10 and the mixing preheater 20 and between the mixing preheater 20 and the steam-reforming reaction 30, respectively. Such two gas guiding plates 60 and 70 are used to maintain the combustion heat transferred from the burner 40 at a proper temperature for the reforming reaction and preheating.
Further, a reformer, disclosed in Korean First Patent Publication No. 1996-0034070, comprises single dual cylinder type tube reforming pipe filled with a reforming catalyst. In this reformer, the reforming pipe is internally provided with a plurality of combustion catalyst layers having a honey-comb structure; a fuel supplying pipe provided in the center of the combustion catalyst layer; and a fuel gasifying coil provided inside and connected to the reforming pipe.
As illustrated by the related examples above, a heater for heating a reformer can typically be classified as one of two types, a catalyst heater that burns a combustion fuel by the catalysis of the combustion catalyst, and a combustion heater (i.e., burner) that burns the combustion fuel by flames.
A catalyst heater typically comprises a combustion catalyst layer; a distributor to uniformly distribute the combustion fuel and oxidant to the combustion catalyst layer; and an igniter to ignite the combustion fuel and air.
In the catalyst heater, heat generated when the combustion fuel and oxygen are ignited by the igniter is used in heating the combustion catalyst layer to its catalyst activity temperature. After the combustion catalyst layer is heated up to its catalyst activity temperature, the igniter stops operating. After the igniter stops operating, combustion of the combustion fuel and oxygen continues due to the catalytic activity of the heated combustion catalyst layer.
After the operation of the igniter is stopped, the igniter continues to be exposed to oxygen and continues to be heated by the heat generated by the catalytic combustion. Accordingly, the igniter is vulnerable to high temperature oxidation due to prolonged exposure to heat and oxygen, which reduces its durability.